A recent trend in wireless communications has been to utilize multiple transmit and/or receive antennas, for example to provide for antenna diversity to improve communication quality. For example, in Multiple-input and multiple-output (MIMO) systems, both transmitter and receiver in a wireless communication system use multiple antennas for communication. Other related topics include antenna polarization diversity, pattern diversity, spatial diversity, smart antennas, adaptive antenna arrays, and adaptive beam forming, for example.
Often, it is desirable to provide adequate radio antenna components within a small package. For example, for portable wireless devices such as handheld cell phones, smart phones, PDAs, embedded wireless devices, peripheral devices such as wireless USB™ adapters, and the like, small size is desirable for reasons such as portability and cost. However, the drive toward smaller size may conflict with the drive toward multiple antennas, since more antennas typically require more space.
U.S. Pat. No. 5,532,708 discloses a compact dual mode antenna which includes a single compact radiating structure and an electronic switch for driving the radiating structure either as a split dipole antenna or as a top-loaded monopole antenna, thereby facilitating polarization and pattern diversity. However, a drawback of this design is that only one excitation mode may be used at a time.
U.S. Pat. No. 6,529,749 discloses a compact multi-band antenna which can be selectively driven in different configurations. In a first configuration, first and second conductive branches can jointly radiate as a dipole antenna, while in a second configuration the first and second conductive branches can be operated separately as inverted-F antennas, or they may radiate independently as monopole antennas. Again however, a drawback of this design is that only one excitation mode may be used at a time.
U.S. Pat. No. 7,012,568 discloses a multiresonant antenna structure having various resonant modes which share at least portions of the structure volume. The basic antenna element has a ground plane and a pair of spaced-apart conductors electrically connected thereto, with additional elements coupled thereto by stacking, nesting, or juxtaposition in an array. However, the multiresonant antenna structure is designed to increase overall bandwidth, with different configurations used at different times.
In addition, the above approaches are limited to specific configurations and arrangements of antenna elements, which may not be suitable for some applications, for example due to their physical, electrical and/or electromagnetic characteristics. For example, the above approaches may not be suitable for supporting one or more of: desired polarization diversity, a desired radiation pattern, and a desired physical form factor.
Therefore there is a need for a compact multi-antenna, compact multi-antenna system and wireless device comprising same that is not subject to one or more limitations of the prior art.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present technology. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present technology.